For treatment of various diseases in the body, catheters and cannulas are widely used. Using cannulas, a drug can be injected into the tissue whereby the drug is placed in the tissue to be absorbed by diffusion into the tissue cells and subsequently distributed throughout the body using blood as a carrier. Often it is necessary to infuse a drug or substance into the vascular system of the body to treat a specific area of the vascular system. For example, after balloon angioplasty, certain drugs are infused to reduce the risk of re-stenosis of the lesion. These drugs are placed around the lesion to be absorbed by diffusion to the tissue around the lesion. Due to the constant flow of blood in the vessel, the drug infused often gets washed away and only a small amount of the drug is absorbed by the tissue.
In the past, many inventors have tried to solve this problem by providing different solutions. One such method is to use two balloons to occlude the vessel on either side of the lesion (the area of interest) and provide a pool of the drug at the lesion to be absorbed by the tissue by diffusion. This method has the drawback that during balloon inflation, the blood supply is stopped and causes ischemic manifestation to the organ that is supplied by the blood vessel that is to be treated.
Several other devices have also been developed where the drug is infused under pressure to the issue, using balloons.
In another invention, the balloon has small microscopic holes and the balloon is inflated using the drug. The drug is then injected to the tissue through the holes after inflating the balloon.
Others include double-wall balloon where the inner balloon is inflated using an inflation medium while the drug is infused through microscopic holes that are in between in the outer and inner balloon walls.
Various such devices are described in the article by Dr. Steve Bailey in THE JOURNAL OF SEMINARS IN INTERVENTION CARDIOLOGY--LOCAL DRUG DELIVERY, Vol. 1, Issue 1, March 1996, pp. 17-23; by Christine Enger on pp. 27-33; by Mun Hong, pp. 34-35; by Aaron Kaplan, pp. 36-38; by Edoardo Camerzind, pp. 39-40; and by Peter Barath, p. 43.
In most or all of the above cases, a balloon is involved in the delivery of the drug. As a balloon is used as the tool, it invariably causes the occlusion of the artery, which causes ischemic conditions in the organ that is supplied by the blood vessel. This means that the balloon must be deflated quickly after inflation to cause injection of the drug. In all these instances, the drug absorption takes place by diffusion, which is a very slow process.
Another method developed is the needle catheter. The needle catheter is a device having four needles that can be advanced through a tube to protrude outwards to inject the drug into the wall of the blood vessel. These catheters are often bulky and, due to the fact that the needles are metal and stiff, cause damage to the blood vessel wall during the procedure.